A VALVE UNIT WITH A SENSOR DEVICE FOR MONITORING THE POSITION OF A PLUG ON ITS OPERATING PATH WITH RESPECT TO A CORRESPONDING VALVE SEAT, PARTICULARLY FOR SUPPLYING GAS THROUGH A GAS METERING APPARATUS

What is described is a valve unit for controlling the supply of a combustible gas, particularly through a gas meter, of the type comprising a plug (4) associated with a corresponding valve seat (3), the plug being fixed to an operating rod (5) which is movably guided by an actuator means from and towards the valve seat (3) along an operating path defined by at least two opposing end positions, and a position sensor device (10) of the Hall effect type, associated for operation with the plug (4) to detect the position of the latter along the path with respect to a static structure of the valve unit, the sensor (10) including a first part fixed to the static structure and a second part fixed to the operating rod (5) of the plug. The Hall effect sensor device (10) is of the magnetic type and one of the first and second parts comprises the sensing element of the sensor (10) and the other of the parts comprises a first and a second pair (14, 15) of magnetic dipoles, each pair including a first and a second magnetic dipole (14a, 14b; 15a, 15b), each of opposite polarity, separated by a corresponding transition zone. The corresponding transition zones are positioned at the corresponding end positions of the path, and magnetic charges of the dipoles of the first and second pair (14, 15), which are adjacent to and face each other, along the path, have the same polarity.